Make brownie batter according to directions on box. Stir in 1/2 cup chopped Andes mints.
Transfer batter to a greased 9×13-inch pan. Bake according to directions on box. Let cool.
In a large bowl, use a hand-held mixer to beat cream cheese, powdered sugar, and peppermint
extract until smooth and creamy.
Stir in Cool Whip and a few drops of green food coloring.
Stir in chopped Andes mints. Spread mixture on top of brownie layer.
In a large bowl, whisk together pudding mix and milk until it is smooth and starting to thicken.
Pour over cream cheese layer. Cover and refrigerate until pudding is fully set.
Spread Cool Whip on top and sprinkle with chopped Andes mints just before serving.
(The mints will bleed into the Cool Whip and discolor it if you add them too far in advance.)